MIC's fans watched as Louise admitted to her boyfriend Andy in the finale episode that she had visited the guy at his place before staying there over night. Andy, meanwhile, had thought she was meeting the man for a drink before heading home.
Although Andy accepted Louise's apology - and her pleas that it was all innocent - Lucy made a comment on Twitter that appeared to be aimed at her.
The reality star, who is now dating Louise's ex-boyfriend Spencer Matthews, said: "I don't understand why people get in to relationships if they're just going to f*** it up. #selfish."
Louise, meanwhile, stayed silent following the episode, as did Andy. Twitter, however, was rife with rumours about who the man was that Louise had been with.
Last month, it was reported that Louise had spent the night with One Direction star Niall Horan, and many fans suggested it could be related.
At the time, when approached by Reveal, Louise's rep declined to comment and Niall's spokesman didn't respond.